Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	$ 74	$ 75
Duke Energy Carolinas
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	19	19
Progress Energy
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	17	19
Duke Energy Progress
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	6	6
Duke Energy Florida
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	11	12
Duke Energy Ohio
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	21	22
Duke Energy Indiana
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	5	6
Piedmont
Environmental Matters Details [Line Items]
Reserves for Environmental Remediation	$ 12	$ 10